The present invention relates to a device for producing effluent contained in a submarine geological formation and a production method implemented by means of such a device. It applies in particular to submarine transfer of petroleum output over short and medium distances, for example between a hydrocarbon deposit and a hydrocarbon processing platform located over a larger deposit developed previously.
The devices for producing the effluent contained in a submarine geological formation that are usually employed in oilfields, include at least one drilled well, each of said wells extending from a low end in a hydrocarbon reservoir to a high end forming a wellhead located essentially above the seabed, at least one of said wellheads being connected to a production line feeding into a processing zone such as, in particular, a platform. A rig of this type is described in particular in U.S. Pat. No. 4,152,088.
In such types of offshore production, the use of electric pumps, or a gas injection process commonly known as "gas-lift", is known to improve extraction of effluents from the formation and to facilitate transfer to a remote platform. These assisted production processes are expensive in both outlay and operation.
Hence, the goal of the present invention is to overcome the above drawbacks by providing a less expensive effluent production device which benefits from ease of use, particularly in terms of damaged parts replacement.
The source idea of the present invention is to propose a device and a method using a jet pump, also called ejector pump, located essentially on the seabed, at the outlet of the wellhead or after a group of valves (manifold) which allows the output from several wells to be grouped to improve extraction of effluents from a submarine geological formation and permit transfer to remote processing facilities.
A jet pump which can in particular be used as part of the present invention is of the type described in French application No. 87/08.919 filed by the present applicant. This pump allows fluids to be raised in a well through the inside of the tubing and, in addition to the lower installation, maintenance, and operating cost, and its ruggedness ensures great operating reliability superior in particular to that of electric pumps. In addition, such pumps allow improved conservation of pumping energy output under multiphase intake conditions when the relative quantities of gas and liquid to be recompressed vary. Finally, these pumps allow good regulation flexibility as a function of the intake conditions, particularly by adjusting the flowrate of the drive fluid, a short reaction time when the settings are changed, and good ability to pump viscous, corrosive, or caking fluids.
Thus, the goal of the present invention is an effluent production device contained in a submarine geological formation having at least one drilled well, each of said wells extending from a low end in a hydrocarbon reservoir to a high end forming a wellhead located essentially above the seabed, at least one of said wellheads being connected to a production line feeding into a processing zone such as, in particular, a platform, characterized by also having a pumping module located on the seabed provided with a jet pump connecting the wellheads to the production line, with the hydrocarbon being pumped from the wellhead outlets to the storage zone by said jet pump.
The present invention is particularly useful when used with the pumped tools and instruments technique usually known by the initials TFL (from the English "Through Flow Line.") This technique makes it possible to install or remove one or more jet pumps as desired to adjust their setting parameters or carry out inspection and maintenance operations.
In one particular embodiment, the effluent production device is characterized by at least one of the wells having a jet pump located at a given depth inside the well in order to pump the effluent from the formation to the wellhead.
Such a device enables a geological formation to be worked in a flexible manner appropriate to each of the wells, particularly when the formation is heterogeneous and has already been worked and decompressed.
After bringing the output from several wellheads into a manifold, a first jet pump may be disposed downstream of this manifold to recompress the entire output. Simultaneously or sequentially, depending on how output of the various wells is developing, one or more jet pumps (one per well) may be placed at the appropriate depth, which is a function of the degree of completion of the wells and the hydrostatic pressure of the effluent, with or at the bottoms of the wells, the hydraulic characteristics of said pumps being matched to the pressures and flowrates of the fluids to be pumped. These jet pumps may be installed and removed by the TFL technique.
A switching device, each of whose branches is connected to one wellhead and whose reunifying element is connected to the jet pump, is placed advantageously upstream of the pumping module disposed on the seabed.
In one particular embodiment, a drive fluid line coming from the processing zone feeds into the pumping module as well as each of the wellheads.
According to a first embodiment, the drilled wells each have coaxial tubing outside a production tube in which a jet pump is disposed, the production tube being connected at the level of the wellhead with a branch of the switching device and the annular volume located between the tubing and the production tube being connected to the drive fluid line.
According to a second embodiment, the drilled wells each have tubing in which is disposed a first tube receiving the jet pump for effluent production and connected at the wellhead to one branch of the switching device, and a second tube connected at the wellhead with the drive fluid line for feeding the jet pump.
The present invention also includes a method for producing effluent contained in a submarine geological formation, implemented in the device as described above, wherein a drive fluid is injected into the fluid line and flows from the platform to the jet pump of a pumping module, with the pumped effluent being collected through the production line and being brought up to the pumping module in the production tube.
Advantageously, the jet pump of the pumping module and the jet pumps located one in each well are controlled simultaneously by the drive fluid line.
In a preferred embodiment, in which the jet pumps are of the pumped tool and instrument type, these pumps are lowered and raised from the platform in the production line toward the pumping module, then toward each of the wells by the switching device.
Advantageously, a tool diameter changing device is used when the pumped tools are lowered inside the pumping module.